I didn't explore this too deeply, but I couldn't get input to work in this scenario, though TextField did. It actually might have nothing to do with ember-simple-auth and devise, but instead be due to my recent transition to Emblem.js, which handles bindings a little differently.

Yeah, just confirmed that when I switch to hbs it works with plain input. I'll have to see what I'm doing wrong with Emblem, but for now, I'll switch the syntax back to the original.